Maybe you've seen one of State Farm's recent commercials. Two guys are walking home from the grocery store, their arms impossibly full of bags. They cross a long bridge and you get the sense that they still have quite a ways to go before they can set down everything they're carrying.
One guy says to the other, "I just saved a ton of money on my car insurance."
The other guy replies, "Wait. You have a car?"
The first guy says, "Yeah. It's an SUV."
And the second guy looks all chagrined, like, Dude, so why are we carrying all these groceries?
It's a mildly funny commercial, but let me tell you what would have made it even more funny - if they had ended it before the last line. "Wait. You have a car?" is the punch line. We don't need anything after that.
By tacking, "Yeah. It's an SUV" on the end, the advertisers are waving in our faces. It's like they're saying, "Hey, did you get it? We made a funny. Isn't it a horrible piece of irony that not only does he have a car, but it's huge? Like, he's totally walking miles with his food and he doesn't have to. Get it? Get it? Ha ha ha ha!!" The audience isn't being allowed to feel the humor for themselves - they're being commanded to feel a certain way instead of choosing to feel it.
And I've seen this a lot in books.
If you're writing comedy, let the joke float into the air on its own and come to rest gently on the mind of the reader. Let them realize it's funny. If you make a big deal out of it, you're in essence acting just like Uncle Bob, who slaps you on the back every time he says something he thinks is funny. "Get it? Get it? It's a joke."
If you're writing an emotional scene and you want the reader to feel emotional too, don't layer it on so thick that the reader has to dig out of it with a shovel. Show them why they should feel sad and show honest reactions from the characters, and then step back and trust the reader's imagination to take them the rest of the way.
Know when you've done enough, and know when to stop.